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Thread: Grinding wheel

  1. #31
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    Quote Originally Posted by Ueee View Post
    Having been screwed around by pretty much every major abrasive company in Aus i bought a couple of diamond wheels out of China, these have exceeded my expectations by miles and cut so much cooler and more freely than the SiC wheels. The biggest issue is dressing them!
    According to a post seen somewhere on PM, diamond wheels used on a SG can be trued by grinding a piece of steel, which removes, or somehow "absorbs" projecting diamonds. This is consistent with the general dictum that diamond wheels are not effective for grinding HSS.

    Regards,
    Bill

  2. #32
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    Bill unfortunately there's a lot of things said on the internet, not all of it is true.

    I find it difficult to believe a piece of steel could be used to dress a wheel, and it sounds like the sort of crap that would come off HSM or similar. The majority of a diamond wheel is either a binder or substrate and not diamonds. I believe high carbon steels are said to react with the diamonds in the wheel at high temperatures and that may cause high rates of wear, but wearing a wheel is not the same as dressing a wheel.

    In regard not being able to use HSS with a diamond wheel, most home shop style tool grinders like the Drill Doctor etc use a diamond wheel to sharpen the HSS drill bits. I have one for example and use it regularly, and have not seen any wear in the wheel.

  3. #33
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    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    I read about grinding HSS as well and i can assure you it does not work, at least not as far as dressing the wheel. It works well if you want to grind the HSS!
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  4. #34
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    My memory is getting a little ratty, so I searched around and managed to find the source of my recollection - Truing Diamond Wheels
    True, there's more to it than touching a bit of steel to a diamond wheel, and different options mentioned, but some fairly dependable posters supporting the contention.

    Bill

  5. #35
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    Quote Originally Posted by WCD View Post
    My memory is getting a little ratty, so I searched around and managed to find the source of my recollection - Truing Diamond Wheels
    True, there's more to it than touching a bit of steel to a diamond wheel, and different options mentioned, but some fairly dependable posters supporting the contention.

    Bill
    Bill, what they said is that high carbon steel will erode a diamond wheel. Whether that's true or not I can't say as I'm not a metallurgist. Just because Forrest Addy says it, doesn't make it true I can promise you on that point. Eroding (ie wearing it) isn't the same as dressing it.

    What I can assure you however is that there are many applications where HSS is ground with diamond, and it doesn't seem to affect the wheel, not in my experience. Whether it's the ideal abrasive to use is another thing, again I can't say, but I can say it's used. The topic of diamond on steel topic comes up relatively regularly and I often use the example of my own Drill Doctor to contend that if HSS wears/destroys wheels as fast as some suggest, how is it I can find no evidence of any wear etc in my wheel. Furthermore, why would a manufacturer specifically use a diamond wheel for grinding HSS? Drill Doctor Fine Diamond Sharpening Wheel - 180 Grit

    What MAY be possible is that unhardened high carbon steels or high carbon steels other than HSS may affect a diamond wheel, or even low carbon steels for that matter. I have no idea as I've never tried it so can't say. I guess it's plausible. I have ground HSS on another diamond wheel though. The earth continued to revolve.

  6. #36
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    Without going back to check Pete, I think that one of the posters said that running the wheel slower when dressing had an effect on the bond, ( I guess making it softer), and not the diamond as such, whereas running it at full speed made the bond perform as one would expect. I will have to re-read tomorrow, as the cot beckons after a fairly big day.

  7. #37
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    From my understanding the diamond breaks down only at high temperatures ie greater than 700-800 C, so it could be that running the wheel slower keeps the diamond below this critical temperature. It could also be that the surface speeds of something like the Drill Doctor etc don't allow the wheel to achieve temperatures above that. It's a truly puny wheel they use. I can't say I've ever noticed any sign of sparking, so again I'm just surmising. With nothing more to go on, I'd put all this in the "plausible" basket.

    However, while not outright calling BS on the suggestion that a diamond wheel can be "dressed" with a chunk of mild steel, as I simply don't know, I will say I find it "difficult to believe". Again, just because somebody says something on a forum, doesn't make it true. If I'm not sure I tend to look for reliable sources like academic papers, abrasive manufacturers' literature, or decent journals like Modern Machining etc. When this has come up in the past I've seen it suggested that under certain conditions (ie high heat) steel will wear a diamond wheel at a rate that would be unacceptable for a commercial operation, and I understand that happens at a molecular level. I don't understand what that reaction actually is. But that's not dressing a wheel.

  8. #38
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    Quote Originally Posted by Pete F View Post
    From my understanding the diamond breaks down only at high temperatures ie greater than 700-800 C, so it could be that running the wheel slower keeps the diamond below this critical temperature.
    I think the argument over the diamonds vapourising started with a real concern back in the day when diamonds were expensive thanks to cartel behaviour. Diamond wheels were expensive items and manufacturers that used diamond wheels wanted to get maximum productivity out of said wheel and rightly did not use those wheels on any steel as at the speeds and feeds a manufacturer would run the wheels at, the diamonds would turn into another form of carbon.

    Then the price of diamond wheels dropped massively making the diamond wheels affordable to the home shop crowd and the home shop crowd read it somewhere and completely ignored the maximum productivity reason not to use diamonds on steel and the legend was born that using diamond wheels on steel will kill sperm whales, make baby jesus cry and cause runaway global warming.
    Gold, the colour of choice for the discerning person.

  9. #39
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    Quote Originally Posted by .RC. View Post
    ... and cause runaway global warming.
    Those barst*ds!!

    Michael

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